On the Varietal and Cultural Differences of Ripening Process in Rice Plant

Abstract

Statistical methods to summarize the trend of ripening process were discussed, and the varietal and the cultural differences were compared in view of the quality in rice grains. As the better methods, it was proposed to fit the regression model of intersecting straight line with a plateau to the relationship of the percentage of ripened grains on the accumulated temperature after heading. Applying this method, trends of ripening process were characterized in a few parameters, the increasing rate of percentage of ripened grains just after heading (b), the accumulated temperature attaining to plateau of percentage of ripened grains (X) and the value of plateau of percentage of ripened grains (Y). Comparing those characteristics between varieties and between methods of fertilizer application by means of analysis of variance, (b) and (X) were significant in differences between methods of fertilizer application, while (Y) showed higher variation between varieties rather than between methods of fertilizer application. Analyzing the aspects about ripening process of whole grains into the primary rachis grains and the secondary rachis grains, it was clear that both (b) and (Y) showed significant differences between methods of fertilizer application only in the secondary rachis grains. From those results, it was emphasized that the control of maturation of the secondary rachis grains through the way of cultivation should be important in view of the better quality in rice grains.